Process and apparatus for partial combustion of hydrocarbons



2 Sheets-Sheet 1 FIG. 3

' 'mwzmok. Spencer L. Knapp ATTORNEY x x x x s. 1.. KNAPP FIG. I

Aug. 27, 1968 PROCESS AND APPARATUS FOR PARTIAL COMBUSTION OFHYDROCARBONS Filed Jan. 28, 1966 PIC-3.2

21 1968 s. L. KNAPP 3,399,245

PROCESS AND APPARATUS FOR PARTIAL COMBUSTION OF HYDROCARBONS Filed Jan.28, 1966 2 Sheets-Sheet 2 FIG. 4 FIG. 7

FIG.5 F|G.6 F|G.8 FIG.9

FIG. FIG.I2 F|G.l3

INVENTOR.

Spencer L. Knapp ATTORNEY United States Patent 3,399,245 PROCESS ANDAPPARATUS FOR PARTIAL COMBUSTION 0F HYDROCARBONS Spencer L. Knapp, TexasCity, Tex., assignor to Monsanto Company, St. Louis, Mo., a corporationof Delaware Filed Jan. 28, 1966, Ser. No. 526,680 9 Claims. (Cl. 260679)ABSTRACT OF THE DISCLOSURE A process and apparatus for the partialcombustion of hydrocarbons to such products as acetylene wherein amixture of hydrocarbon and oxygen is passed through a gas distributorhaving means located in the gas distributor tubes for imparting aswirling motion to the gases passing therethrough. Deposition of carbonon the face of the gas distributor is thus reduced.

This invention relates to a process for partial combustion ofhydrocarbons and oxygen and to an apparatus therefor.

It is known to prepare acetylene and other products such as ethylene,hydrogen and carbon monoxide by the partial combustion of gaseous orvaporized hydrocarbons and oxygen. In these known processes, a preheatedgaseous hydrocarbon and a preheated oxygen-containing gas are reacted ina flame reaction and then cooled as by quenching with water. Theapparatus for such a reaction generally includes a mixing chamberwherein the hydrocarbon and oxygen-containing gas are mixed and areaction chamber. The mixing chamber is connected to the reactionchamber by a plurality of channels which conduct the mixed gases fromthe mixing chamber to the reaction chamber wherein the combustionreaction occurs as the mixed gases exit from-the channels.

A particular disadvantage of this process is the deposition of carbon onthe walls of the reaction chamber, particularly on the wall containingthechannel openings, referred to hereafter as the face of the burnerblock. These deposits have to be periodically removed in order tocontinue regular operation of the process.

It is, therefore, an object of the present invention to provide anapparatus and a process for the incomplete combustion of hydrocarbonsand oxygen which can be operated continuously without the disadvantageof having to frequently remove carbon deposits.

Another object of the present invention is to provide an apparatus andprocess for the partial or incomplete combustion of hydrocarbons andoxygen whereby substantially less carbon is deposited on the walls ofthe reaction chamber than in prior art apparatus and processes.Additional objects will become apparent from the following descriptionof the invention herein disclosed.

These and other objects are accomplished by the present invention which,in one of its embodiments, is an apparatus for the partial or incompletecombustion'of a hydrocarbon and an oxygen-containing gas which comprisesa mixing chamber and a reaction chamber, said reaction chamber in opencommunication with said mixing chamber by means of a plurality ofchannels, at least one of said channels containing means for imparting aswirling motion to the gases passing from said mixing chamber into saidreaction chamber, said means being located more than half the distancefrom said mixing chamber to said reaction chamber.

In another embodiment, the present invention is a process for thepartial combustion of hydrocarbons and oxygen which comprises mixing ahydrocarbon and an oxygen-containing gas in a mixing zone, passing theresulting mixture at elevated temperatures and in the gaseous 3,399,245Patented Aug. 27, 1968 ICC form to a reaction zone through a pluralityof channels wherein the gaseous mixture encounters in at least one ofsaid channels a means for imparting a swirling motion to the gases, saidmeans being located more than half the distance from said mixing zone tosaid reaction zone, and partially burning said mixture in said reactionzone.

The term swirling motion as used herein refers to a rotational or spiralmotion in which the path of the motion does not lie in a single planeand in which the path followed by the motion describes a cone. The termswirlers as used herein refers to the means within the channels forimparting swirling motion.

To further define the present invention, reference is made to theaccompanying diagrammatic drawings of different views and embodiments ofthe present invention. The same reference characters are used in each ofthe drawings to denote like features of the apparatus of the presentinvention.

FIGURE 1 is a sectional view of an apparatus used for mixing andreacting hydrocarbons in accordance with the present invention.

FIGURE 2 is a sectional view of a channel connecting the mixing andreacting chambers without any means for imparting swirling motion to thegases passing therethrough.

FIGURE 3 is a sectional view of a channel containing means for impartinga swirling motion to the gases passing therethrough.

FIGURES 4 through 13 are drawings of various embodiments of the meansused to impart a swirling motion to the gases exiting from the channelsof the apparatus of the present invention.

Referring specifically to FIGURE 1, preheated oxygen oroxygen-containing gas enters mixing chamber 1 through line 2 where itmeets and is mixed with a stream of preheated gaseous hydrocarbonintroduced through line 3. From mixing chamber 1, the mixed gases passthrough -a burner block 4 by means of channels 5. In channels 5, thegases encounter a swirler 6 which imparts a swirling motion to the gasesas they exit into the reaction chamber 7 where the mixed gases react ina flame reaction. The reaction chamber 7 is bounded by walls 8 and theface of burner block 4. After leaving the reaction chamber 7, the gasesare cooled by quench water 9.

While the apparatus has been pictured in FIGURE 1 as having only threechannels in the burner block, it is to be understood that in actualoperation the apparatus can have varying numbers of channels. Thesechannels may be of various configurations such as round, square, orrectangular. The channels may also be Venturi-shaped. The channels 5shown in FIGURE 1 'are usually substantially parallel with one anotherthough some deviation from such parallel alignment may be permitted.Also, the ap paratus does not have to be operated in the positionpictured so that any reference herein to such terms as up or down areonly relative to the apparatus as shown.

It has been found that means inserted within the burner block channelsto provide a swirling motion in accordance with the present inventionsubstantially prevents carbon deposits from forming on either the Wallsof the reaction chamber or around the channel exits on the face of theburner block. Further, the motion imparted by the swirlers causes thegases to have a greater angle of expansion than those gases exiting froman unobstructed channel as is illustrated in FIGURES 2 and 3 describedbelow.

FIGURE 2 is a sectional view of a channel 5 within the burner block 4and shows the angle of expansion 01 of the gases exiting from anunobstructed channel. FIGURE 3 is a sectional view of channel 5 in whicha means 6 for imparting swirling motion is located and is intended toshow the angle of expansion b of the exiting gases is greater than theangle of expansion a obtained by the corresponding channel without aswirler.

The swirlers encompassed by this invention may have various shapesandconfigurations as long as they impart swirling motion to the gasesexiting from the channels. In a particularly useful embodiment of thepresent invention, the swirler comprises two surfaces of substantiallythe same size and configuration within a channel, both surfaces beinginclined at substantially equal angles of less than 90 with respect tothe vertical or longitudinal axis of said channel but being inclined insubstantially different directions with respect to one another such thatthe segments of the two surfaces lying within a transverse .orhorizontal plane of said channel are substantially perpendicular to andon opposite sides from one another of a straight line lying within saidplane passing through the axis of said channel. The inclined surfacesare preferably flat though they may also be curved either longitudinallyor transversely. For optimum results, the edge of the inclined surfacesnearest the walls of the channel, usually referred to as the outer edge,should be substantially contiguous with the wall of the channel. Also,the two inclined surfaces are usually located approximately equidistantfrom the exit end of the channels.

The above-defined particularly useful embodiment of the swirlers of thepresent invention is further described and illustrated by FIGURES 4through 13 which show various shapes that swirlers may take within thisembodiment.

FIGURES 4 through 6 are pictorial drawings of a swirler designed inaccordance with the above-defined particularly useful embodiment of thepresent invention. FIGURE 4 is a top view of FIGURE 5 while FIGURE 6 isa view of FIGURE 5 as rotated 45 to the left. The swirler includes twoinclined surfaces and 11 each of which, when placed in a channel, willdivert the gases downward along the inclined surfaces thereby impartinga swirling motion to the gas exiting from the channel. The angle crepresents the angle; the surfaces are inclined with respect to the axisof the channel.

The swirler of FIGURES 4 through 6 may be readily fabricated from sheetmetal or other suitable material and inserted into existent burner blockchannels. For instance, a strip of sheet metal, the end of which hasbeen rounded to fit the inside ofa channel, can be split lengthwise fora small distance than that portion of the strip on each side of thesplit bent in opposite directions at the desired angle as shown inFIGURES 4 through 6. If desired, the portion of the strip of sheet metalwhich is not split and bent will form a shaft which may be used tosuspend the swirler within the channels. FIGURES 5 and 6 show this shaftcut off immediately above the swirling surfaces 10 and 11.

FIGURES 7 through 9 are pictorial drawings of another swirler designedaccording to the above-defined particularly useful embodiment of thepresent invention. FIG- URE 7 is a top view of FIGURE 8 while FIGURE 9is a view of FIGURE 8 as rotated 45 to the left. This swirler, like thatof FIGURES 4 through 6, has two surfaces 12 and 13 which direct the gasdownward and in a swirling motion. This swirler differs from that ofFIG- URES 4 through 6 in that the surfaces 12 and 13 are bent.

The angle at which the inclined surfaces of the swirlers are inclinedwith respect to the longitudinal axis of the channel, shown in FIGURE 5as angle 0, for the type of swirlers shown in FIGURES 4 through 6 and 7through 9 generally is between 15 and 40, and preferably is to 35. Theoptimum angle will depend on such variables as the gas velocity, theposition of the swirler within the channel, and the channel diameter andlength. Too great an angle of inclination will result in too large apressure drop through the channel and is preferably avoided.

The swirlers .of FIGURES 4 through 6 and 7 through 9 are of the typewhich may be suspended within the channels of existent burner blocks.However, a burner block may be fabricated which has the swirler builtinto the channels. For example, a burner block may be fabricated bycasting a refractory material around ceramic tubes which have swirlersmolded within the tubes. The insides of these tubes form the channelsfor the passage of gases from the mixing chamber to the reactionchamber. A channel with a built-in swirler is shown in FIGURES 10through 13. FIGURE 10 is a top view of FIGURE 11 while FIGURE 12 is aview of FIGURE 11 rotated 45 to to'the left and FIGURE'13 is a side viewof FIGURE 11. As may be seen from the illustration, the swirler isformed by two semi-elliptical shaped surfaces 14 and 15 inclined atopposite angles with respect to one another within the tube. Thesesurfaces are formed by (l) a first substantially flat surface extendingat an inclined angle across or substantially across onehalf thecross-sectional area of the channel, this first surface being inclinedat an angle of less than with respect to the axis of the channel asindicated by angle d in FIGURE 13 and (2) a second substantially flatsurface having no common line of intersection with said first surfaceextending at an inclined angle across that part of the channelcross-sectional area not containing said first surface, the secondsurface being inclined with respect to the axis of the channel in adirec tion different from the first surface, and the angle ofinclination of the second surface with respect to the axis of thechannel being the same as that of the first surface. If both surfacesare the same distance from the channel exit which is preferred, thenboth would include a straight line passing perpendicularly through theaxis of the channel. In this type swirler, as in the other typesillustrated, the optimum angle of inclination of the surfaces depends onfactors such as channel diameter and length. This type of swirler,however, is generally inclined less with respect to the channel axisthan those of the type shown in FIG- URES 5 and 8, the angle ofinclination generally being from 10 to 25", preferably 12 to 18.

The exact location of a swirler within the channels of the burner blockwill vary with the type swirler used, the channel diameter, the channellength, and the like. Positioning the swirler too close to the exit ofthe channel may result in flame instability due to the extremeturbulence of the exiting gases, while a swirler located too far fromthe channel exit will not affect the exiting gases sufiiciently toprevent carbon deposits from forming. However, it has been found thatthe swirler must be located in the lower half of the channel, i.e., morethan half the distance from the channel entrance to the channel exit ormore than half the distance from the mixing chamber to the reactionchamber.

Another type of swirler within the above-described particularly usefulembodiment of the present invention may be obtained by rotating one endof a fiat strip of flexible material while maintaining the other endsubstantially stationary and fixing such strip in the form so obtained.The amount of rotation would, of course, depend on the amount ofswirling motion which is desired as well as such factors as the length,width, and thickness of the flexible strip, the location of the strip inthe channel, the gas velocity, etc.

It is again emphasized that the means to impart a swirling motion to thegases is not limited to the foregoing embodiment, i.e., two inclinedsurfaces. It will be apparent to one skilled in the art that othervarious means may be devised to impart a swirling motion to the gasesexiting the channels. For example, a screw-shaped object as is formed bya continuous helical surface projecting from a central shaft or spindleor from the walls of a channel will provide a single continuous surfaceto direct gases downward and in a swirling motion if such object isplaced within a tube or channel. Also, rotating spinners supportedwithin the channels will impart a swirling motion to the gases. It is,of course, within the scope of the present invention that differenttypes of swirlers may be used in different channels of the sameapparatus.

The number of channels in which swirlers are placed will, of course,vary with the number of channels within the burner block being used, thereduction of carbon deposits desired and other considerations.Generally, swirlers will be placed in all of the channels in order toinsure optimum results. However, the deposition of carbon may be reducedwhere onlypart of the channels in the burner block containswirlers.

The following example is given in order to illustrate but not to limitthe invention.

EXAMPLE 1 An apparatus as pictured in FIGURE 1 containing 127 tubes orchannels which were 6% inches in length was used in this experiment.Approximately 4,050 pounds per hour of natural gas preheated to 600 C.was introduced into the mixing chamber of the apparatus where it wasmixed with approximately 4,750 pounds per hour of oxygen also preheatedto 600 C. The mixture of gases, which contained 37 mole percent oxygen,was then passed through the channels, each of which was fitted withmetallic swirlers of the type shown in FIGURE 5. The inclined surfacesof the swirlers were inclined at an angle of 29 with respect to the axisof the channel and had a height as measured longitudinally of thechannel of inch. The bottom of the swirlers inclined surfaces were 1 /2inches from the exit of the channel. After passing through the channels,the gaseous mixture was reacted in a flame reaction and then quenchedwith water. The afiiuent gas contained 8.2 mole percent acetylene, 52.0mole percent hydrogen, 29.0 mole percent carbon monoxide, 0.5 molepercent ethylene and 3.7 mole percent carbon dioxide with the remainderbeing unreacted feed components. The apparatus was operated one weekwith no deposition of carbon on either the walls of the reaction chamberor on the face of the burner block. With the particular swirlers used inthis experiment, the gases exiting from the channels had an angle ofexpansion of 38 degrees on entering the reaction chamber.

Operation of an apparatus as described above except with no swirlers inthe channels and under the conditions described above resulted insubstantial deposition of carbon on the walls of the reaction chamberand on the face of the burner block within a one week period. With noswirlers in the channels, the gas exiting from the'channels had an angleofexpansion of about 26 degrees.

The preferred hydrocarbon used in the process of this invention ismethane; however, various other hydrocarbons are suitable. such asethane, propanes, butanes, and pentanes, etc., including parafiinichydrocarbons of carbon atoms and higher. Ordinarily, the hydrocarbonwill be a paraflinic hydrocarbon with less than 7 carbon atoms. Naturalgas, comprising essentially methane, is a preferred hydrocarbon feedstream for use in this invention.

The oxygen-containing stream which is mixed with the hydrocarbon streamis preferably oxygen; however, any oxygen-containing stream such as airor oxygen-enriched air can be used.

Pressure is not critical in the partial combustion of hydrocarbons forproducing products such as acetylene. The converter operates atessentially atmospheric pressure under normal conditions but alsooperates satisfactorily as high as 40 p.s.i.a. and higher and as low as5 p.s.i.a. and lower, the preferred range being from 10 p.s.i.a. to 24p.s.i.a.

Although preheating of the feed gases to between 500 C. and 600 C. ispreferred for best results, the scope of this invention includespreheating feed gases from about 400 C. to as high as 800 C. and higher.

In the manufacture of acetylenes, the combustion of the gas mixture mustdevelop temperatures in the range of about 1200" C. to about 1800 C.Although it is possible to carry out the combustion and conversionreactions at temperatures higher than 1800 C., optimum results are notobtained due to the production of large quantities of carbon or coke. Attemperatures below the above range, conversions obtained from thecombustion reaction are too low. The preferred range within the reactionchamber is from about 1400 C. to 1600 C.

What is claimed is:

1. An apparatus for the partial combustion of a hydrocarbon and anoxygen-containing gas which comprises a mixing chamber and a reactionchamber, said reaction chamber in open communication with said mixingchamber by means of a plurality of channels, said channels containingmeans for imparting a swirling motion to the gases passing from saidmixing chamber and into said reaction chamber, said means being locatedbetween the midpoint of said channels and said reaction chamber.

2. The apparatus of claim 1 wherein said means for imparting a swirlingmotion comprises two surfaces of substantially the same size andconfiguration, both surfaces being inclined at substantially equalangles of less than degrees with respect to the longitudinal axis ofsaid channel but being inclind in substantially different directionswith respect to one another, both surfaces being positioned with respectto one another such that the segments of the two surfaces lying within atransverse plane of said channel are substantially perpendicular to andon opposite sides from one another of a straight line lying within saidplane passing through the axis of said channel.

3. The apparatus of claim 1 wherein said means for imparting a swirlingmotion comprises (1) a first substantially fiat surface extending at aninclined angle substantially across one-half the cross-sectional area ofthe channel, said first surface being inclined at an angle of less than90 degrees with respect to the axis of the channel and (2) a secondsubstantially fiat surface having no common line of intersection withsaid first surface, said second surface extending across that part ofthe channel crosssectional area not containing said first surface, saidsecond surface being inclined with respect to the axis of the channel ina direction different from said first surface, the angle of inclinationof said second surface with respect to said axis of said channel beingthe same as that of said first surface, and both said first surface andsaid second surface including a straight line passing perpendicularlythrough the axis of the channel.

4. A process for the partial combustion of hydrocarbons and oxygen whichcomprises mixing a hydrocarbon and an oxygen-containing gas in a mixingzone, passing the resulting mixture at elevated temperatures and in thegaseous form to a reaction zone through a plurality of channels whereinthe gaseous mixture encounters in said channels means for imparting aswirling motion to the gases, said means being located between themidpoint of said channels and said reaction zone, and partially burningsaid mixture in said reaction Zone.

5. The process as described in claim 4 wherein said means for impartinga swirling motion comprises two surfaces of substantially the same sizeand configuration, both surfaces being inclined at substantially equalangles of less than 90 degrees with respect to the longitudinal axis ofsaid channel but being inclined in substantially different directionswith respect to one another, both surfaces being positioned with respectto one another such that the segments of the two surfaces lying within atransverse plane of said channel are substantially perpendicular to andon opposite sides from each other of a straight line lying within saidplane passing through the axis of said channel.

6. The process as described in claim 4 wherein said means for impartinga swirling motion comprises (1) a first substantially flat surfaceextending at an inclined angle substantially across one-half thecross-sectional area of the channel, said first surface being inclinedat an angle of less than 90 degrees with respect to the axis of saidchannel and (2) a second substantially flat surface having no commonline of intersection with said first surface, said second surfaceextending across that part of the channel cross-sectional area notcontaining said first surface, said second surface being inclined withrespect to the axis of the channel in a direction different from saidfirst surface, the angle of inclination of said second surface withrespect to the axis of said channel being the same as that of said firstsurface, and both said first surface and said second surface including astraight line passing perpendicularly through the axis of the channel.

7; The process of claim 4 wherein said hydrocarbon is natural gascomprising essentially methane and wherein said process is for theproduction of acetylene.

8. The process of claim 4 wherein said partial combustion takes place atfrom 1200 C. to 1800 C.

9. The process of claim 4 wherein said partial combustion takes place atfrom 1400 C. to 1600 C.

References Cited DELBERT E. GANTZ, Primary Examiner.

J. D. MYERS, Assistant Examiner.

